Study On The Dynamics Of Jack - Up Of Self - Elevating Drilling Platform

As the land-based oil and gas resources are reducing gradually, countries are all accelerating the development process of offshore oil and gas resources. With the offshore oil resources’exploring and drilling positions are making progress from coastal waters to deep waters, the offshore platforms need to face worse operating environment and conditions because of the increasing working depth. Therefore, a variety of offshore platforms are emerged to suit different working environment. And this in turn put forwards higher requirements to the design and construction of offshore platforms. Jack-up platforms are widely used in300m depth coastal waters because they need less manufacturing cost, easy to transport, has a good adaptability to various seafloor topography and can working stably in all sea conditions.The complete migration process of jack-up platforms including in-situ drop ship, pull up legs, tow to the new wells, pitching pile and lift hull, ballast. Among the migration process, pulling legs is the most difficult, high-risk and time-consuming part. In the process of pulling the pile, the legs are under complex forces. And as the elongated part of the platform system, the legs’ flexibility will affect the movement of the whole system. In the design and development process of jack-up platforms, legs as the important component that support the platform working on the sea, its mechanical strength and safety are the important factors to ensure the service life and the safety of the platforms. This paper studied on the dynamics analysis during the pile pulling process of the most widely used jack-up platforms, the main contents are as follows:(1) Took the three legs jack-up platform as the study object, designed the driveline of the lifting device on the platform.(2) Combining used the Pro/E, ANSYS and ADAMS software to build the lifting device, platform hull, truss leg and cylindrical leg models, built the dynamic simulation model of truss legs jack-up platform and the cylindrical legs platform including the hull, legs and the lifting devices.(3) Analyzed the main forces on the platform during the pile pulling process, simplified and simulated the main forces and boundary conditions during the platform pile pulling process. Achieved to simulate the pile pulling process of the platform in ADAMS software by using the sensors and script controls.(4) Used the ADAMS software to do the rigid body dynamics analysis of the truss legs jack-up platform’s pile pulling process, and then did the rigid-flexible coupling analysis by setting the legs as flexible bodies. Got the movements and vibration characteristics of the platform when the platform was under different velocities and the legs were set as rigid or flexible body. Analyzed the influences on the movement of platform when considered the flexibility of truss legs. The results show that the platform will vibrate at the beginning of the drop ship stage and the platform’s vibration amplitude after the legs are pulled up is less than the rigid analysis when considered the legs’elastic. (5) Got the platform’s velocity, acceleration and the force curves by simulating the pile pulling process of the truss legs platform in ADAMS. Import the force curves of the truss leg into ANSYS to do the transient dynamic analysis, got the truss legs’dynamic load analytical results during the pile pulling process. The results show that the truss legs can meet the strength requirements during the pile pulling process.(6) Set the cylindrical legs as flexible bodies to do the rigid-flexible coupling analysis of the cylindrical legs jack-up platform’s pile pulling process. Got the vibration characteristics curves of the cylindrical legs platform. Obtained the stress and strain information of the flexible cylindrical legs by ADAMS. The results show that the cylindrical legs can meet the strength requirements during the pile pulling process.